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Restoration & Repair Tips Board

1948 Ferguson TO-20 Electrical System

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Posted by Randy Roberson on October 23, 2012 at 08:52:59 from (

Hi, I'm finally getting my tractor running again, now that the weather has cooled off. The electrical system was converted to 12V negative ground some years ago, and it is about 1/2 missing. There is a solenoid switch mounted on the battery tray, and a ballast resistor in the circuit to the ignition coil. Rather that spend time restoring it to positive ground, etc. I am just trying to get her running for now.I have bought and installed the reproduction switch which is activated by the shift lever, and I plan to use it in place of the old starter button, along with the solenoid, so at least I will have the neutral safety feature this provides.
What is the correct polarity to install the ignition coil for negative ground: neg to dist, or pos to dist? I think neg to dist, is this correct? It is a 12 Volt coil.
I also am trying to connect the ballast resistor bypass on the solenoid for more ignition voltage during cranking: is this as simple as it looks (connect this terminal on the solenoid to the coil side of the ballast resistor)?
Also, I will probably do away with the key switch (On-Off) as it is broken, and use a toggle switch. Any problem, functionally speaking? I might include a pilot lamp as a reminder to leave the switch off. Depends on if I get her running pretty soon, etc. Thanks for all the advice!


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